This application claims the priority of German Patent Document No. 10039794.8, filed Aug. 16, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a positional adjustment apparatus for a steering column, especially of a motor vehicle. Preferred embodiments relate to a positional adjustment apparatus for a steering column for a motor vehicle, having a tubular jacket fixed on two rails disposed substantially opposite one another, the rails extending in an axial direction of the tubular jacket and having slots extending in the axial direction for longitudinal adjustment of the steering column, and clamping bolts being provided that are guided through the slots in the rails and extend substantially in a radial direction away from the tubular jacket, at least one clamping bolt passing through a rail for vertical adjustment, and it being possible for the longitudinal and vertical adjustments to be secured and released by an operating lever.
A motor vehicle steering column customarily comprises a column jacket, a steering shaft which is rotatably supported on the column jacket, and a steering wheel affixed to the steering shaft. If the column jacket can be swung upwards and downwards to adjust the vertical position of the steering wheel, the steering column is described as rake-adjustable. If, however, the length of the column jacket can be changed in order thus to adjust the horizontal position of the steering wheel, the steering column is described as telescopically adjustable.
Positional adjustment apparatus for rake-adjustable and/or telescopic steering columns are known from industry use in which a pair of vertical sides of a stationary support are clamped by a lift-actuated screw or by a lifted-actuated twist cam on the column jacket in order to secure, by friction, the position of the column jacket relative to the vehicle bodywork.
German Published Patent Application DE 198 05 289 (corresponding U.S. Pat. No. 5,787,759) has also disclosed a rake-adjustable and telescopic motor vehicle steering column having a column jacket consisting of an upper and a lower column jacket, each of tubular shape, the lower column jacket overlapping the upper telescopically. The column jacket is vertically pivotable on the bodywork in order to adjust the vertical position of the steering wheel. Similarly, the upper column jacket can be adjusted horizontally relative to the lower. A positional adjustment apparatus between the upper column jacket and the bodywork secures the horizontal and vertical positions of the upper steering column and hence the horizontal and vertical positions of the steering wheel. An adjustment shaft of the positional adjustment apparatus extends through vertical and horizontal slots respectively above and below the column jacket, as a result of which a rake-adjustable and telescopically adjustable steering column is provided. If the adjustment lever of this adjustment apparatus is in its unlocked position, the column jacket can be adjusted freely both vertically and horizontally.
It has proved to be a disadvantage of this configuration of positional adjustment apparatus that the adjustment shaft is always above or below the column jacket, and therefore requires a great deal of vertical structural space.
A further position lock for an adjustable motor vehicle steering column disclosed by European Patent Document EP 0 493 181 D1 (corresponding U.S. Pat. No. 5,213,004) suffers from the same disadvantage, a bolt guided over the tubular jacket again being provided for the position lock and requiring a great deal of additional structural space.
A clamping apparatus for an adjustable column which requires less structural space, especially vertically, is proposed in German Patent DE 195 07 0900. This patent describes a clamping apparatus in which a tubular housing, adjustable in the direction of its longitudinal axis, can be fixedly clamped between two holders fixed in the bodywork by a clamping mechanism having an axially tensionable clamping bolt passing through the two holders transversely to the longitudinal axis of the tubular housing. The tubular housing receives a steering shaft, the clamping bolt enclosing in an annular manner the steering shaft disposed in the tubular housing and being disposed with its longitudinal axis in the region of the cross section of the tubular housing.
With such a clamping apparatus, however, it has proved to be a disadvantage that the clamping acts directly on the tubular jacket, which imposes very high requirement in respect of the design of the tubular jacket in order for this not to be adversely affected in the region of this clamping.
An adjustable motor vehicle steering column clamping system which solves this problem is known, for example from PCT application publication WO 97/10136 (corresponding U.S. Pat. No. 5,730,465). In this case an adjustable motor vehicle steering column clamping mechanism for adjusting a steering column is described which has a steering column bearing block with two flanks extending over each side of the outer steering column; each flank containing a slot in order to permit vertical adjustment. Such a configuration requires relatively little structural space in the vertical direction, as the bolts are guided away to the side of the tubular jacket and do not run above or below the tubular jacket.
The releasing and securing of the clamping system in this case takes place by means of a lever, which is connected to the two bolts guided away to the side of the tubular jacket. Each of the bolts in this case is provided with a left-hand and a right-hand thread, so that the threads are of multiple-start form. Fixed on these threads are parts of the clamping mechanism actuating lever, which extend in such a way that the two flanks clamp around the two sides of the outer jacket. The lateral parts of the actuating lever are secured by thread connected to the bolt for clamping purposes, each lateral part of the actuating lever comprising an inner cone that is connected to a butterfly nut screwed onto the bolt. When the actuating lever is twisted, the butterfly nuts on the bolts twist in opposite directions on the thread. In this way the lateral parts of the actuating lever can be moved relative to one another, in order thus to move the butterfly nuts to clamp the two supports together and thus effect the clamping of the steering column. If the actuating lever is twisted in the opposite direction of rotation, the two lateral parts are moved in their opposite direction in order to release the two supports and permit adjustment of the steering device.
It has proved, however, to be a disadvantage of this type of configuration that the actuating lever, during securing and releasing of the connection, results in relatively pronounced expansion and compression of the lateral flanks, which can bring about fatigue in the material. In addition, the provision of the bolts with a multiple-start thread requires a relatively substantial construction effort and is thus also very cost-intensive.
It is therefore an object of the present invention to provide a positional adjustment apparatus for a steering column in which, by relatively simple means, it is possible to secure and release the longitudinal and vertical adjustments of a steering column.
This object is achieved according to certain preferred embodiments of the invention with a positional adjustment apparatus for a steering column of the type referred to initially, wherein securing and releasing of the longitudinal and vertical adjustments is implemented via a cam disc actuatable by the operating lever.
With such a positional adjustment apparatus according to the invention for a steering column, it is possible to provide a simple and strong clamping system in a very shallow structural space, and it has proved particularly advantageous that, as a result of the use of a cam disc actuated by means of the operating lever, a defined stroke for the adjustment of the steering column is provided.
As a result a defined positioning of the actuating or operating lever is provided, in which adjustment is possible in one position whereas in the other predetermined position jamming takes place.
xe2x80x9cCam discxe2x80x9d is here understood as meaning, in each case, a disc having a profile which allows play between adjacent structural elements in a first position of the disc and produces a clamping effect, for example as a result of a raised portion, in a second position.
It has proved particularly advantageous according to certain preferred embodiments of the invention if separate cam discs are provided for longitudinal and for vertical adjustment, and the operating lever actuates a further cam disc mounted centrally relative to these cam discs and interacting therewith. With such a configuration, it is possible to achieve a situation wherein, as a result of different positioning of the actuating lever, a separate stroke can be provided for the two cam discs and hence vertical and longitudinal adjustment can take place separately.
The actuating lever itself here can, in either system, always be guided in a defined manner on the running surfaces of the cam discs.
For better guidance of the clamping bolt, provision may be made for a sleeve to be disposed on the clamping bolt and comprising a disc fixedly connected to the sleeve between a rail and a holder adjacent thereto. This is particularly advantageous if, according to certain preferred embodiments of the present invention, the operating lever for operating the positional adjustment apparatus is also moved in the course of the vertical adjustment movement only, not the longitudinal adjustment, and the various clamping elements are loosely disposed in sequence on the clamping bolt. The sleeve is able reliably to prevent the friction between the clamping bolt and the rails during an adjustment resulting in canting of the clamping bolt. In the case of vertical adjustment movements, the disc can slide along the holder together with the clamping bolt, but not cant. Thus the operating lever is cleanly guided and the risk of functional problems is effectively countered.
If, according to certain preferred embodiments of the invention, the positional adjustment apparatus is to be especially crashproof, but nevertheless to take up as little structural space as possible, the securing of the clamping bolts on at least one side of the tubular jacket can be provided by positive fitting, for example by means of a toothing, while on the other side clamping takes place by friction fitting. As a result of the positive-fitting clamping system, such a design is crashproof, while the friction-fitting permits an economy of structural space.
Further advantages and developments of the invention are apparent from the patent claims, the drawing and the description that follows, in which examples of embodiments of the invention are described in detail with reference to the drawings.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.